The present invention relates to lubricant pumps, and more particularly to pneumatically actuated lubricant pumps.
Pneumatically actuated, reciprocating lubricant pumps are well known in the industry and, as shown in FIG. 1, generally include a pneumatically driven piston assembly 30 within a pump housing 12. The head 32 of the piston assembly fits slidably within a cylinder 18 defined by the pump housing 12. In a single action pump, air is forced into the air cylinder lea behind the piston head 32 to drive the piston forward. Once the piston reaches its forward extreme (i.e. completes its pumping stroke), the air is released; and a return spring 74 returns the piston 30 backward in the air cylinder 18. In a double action pump, the return spring is omitted; and, instead, the piston is forced backward in the air cylinder by air supplied on the opposite side of the piston head. A valve system alternately supplies air ahead of and behind the piston head, causing the piston assembly to reciprocate.
In the past, air has been routed to the air cylinder 18 through the sidewall of the pump housing 12. The air flow passage 23 follows the side wall of the pump housing 12 that surrounds the air cylinder 18. As air compression builds within the air cylinder 18, significant force is exerted against the side wall of the pump housing 12. The location of the air flow passage 23 weakens the pump housing adjacent the air cylinder 18 and may lead to premature failure of the pump 10.